The Z Backscatter van, used by the New York Police Department for the past decade, is a powerful, mobile, paramilitary x-ray machine that literally sees through walls. It can detect people, explosives, drugs, alcohol, cigarettes, and even currency. Although these vans further important public safety goals, the NYPD has done both itself and New Yorkers a disservice in keeping details of the van and its usage under wraps. The secrecy that is necessary for some law-enforcement activity to be effective must always be balanced against the equally important need for democratic policymaking. There may be a case for secrecy here, but the NYPD has not yet made it.

Public scrutiny of the vans, and NYPD resistance to this scrutiny, began in February 2012. Michael Grabell, of the investigative-journalism site ProPublica, requested (via the Freedom of Information Law, or FOIL) that the Department disclose documentation about the van. The Department opposed disclosure, arguing that the information “would reveal criminal investigative techniques or procedures.” Asked about the van on October 13, 2015, New York Police Commissioner Bill Bratton said only that it “falls into the range of security and counter-terrorism activity that we engage in.” Given that the existence of the van is public knowledge, it seems incumbent upon the NYPD—if it wants to maintain this almost-absolute veil of secrecy—to specify how public knowledge of these documents could undermine the van’s utility.

Developed following the September 11 terror attacks and used by the NYPD since at least 2004, the Z Backscatter poses a variety of concerns about which the public should be able to engage in an informed debate.

One concern is personal privacy, because the vans allow the police to examine, among other things, the intimate details of human bodies. Similar machines were removed from airports in 2013 after the FAA Modernization and Reform Act of 2012 required that all TSA body scanners use Automated Target Recognition (ATR), a privacy software that blocks everything but the outline of a person from appearing on the imaging screen. It is possible the NYPD is seeing exactly what the TSA was required to avoid. The NYPD maintains that the vans “are not used to scan people for weapons,” but without more information, the public cannot know how much of a person’s body the vans are able to see.

The vans also pose potentially serious health risks, which the NYPD does not dispute. The vans’ x-ray machine emits a dose of ionizing radiation that is 40 percent greater than what travelers experience when going through an airport scanner. Exposure to this radiation, even in low levels, is linked to an increased risk of cancer. The manufacturer of the vans, American Science and Engineering, Inc., maintains in the product description that the machine itself complies with American National Standard Institute (ANSI) safety standards, and that scan performed by a van moving at at 3 mph and from 5 feet away exposes a person to a dose “well below the ANSI specified limit for accidental exposure.” Still, European Union airports banned these scanners in 2011 “in order not to risk jeopardizing citizens’ health and safety.”

Grabell appealed the Department’s denial of his FOIL request, arguing that portions of the records could be redacted or withheld to protect sensitive information, and renewed his request for disclosure. The NYPD resisted, concerned that disclosure “would reveal non-routine investigative techniques and procedures” that would undermine the vans’ effectiveness in protecting public safety. In response, Grabell modified three of the requests to omit requests for documents that would be related to specific or ongoing use, and included another request seeking the contents of image databases. But the NYPD maintained its initial objections.

In December 2014, New York State Supreme Court Judge Doris Ling-Cohan ordered the NYPD to disclose certain information about the vans: summary reports of past deployments; policies, procedures, and training materials for the van; total cost and number of vans; and any tests or reports regarding health effects. The court also required that the NYPD report on the existence of any policies governing retention and storage of data. In ordering these disclosures, the court acknowledged the Department’s concerns that disclosure would reveal specific “techniques and procedures” or “endanger the life or safety of NYPD officers,” but found that in the absence of any specific factual showing to this effect, the disclosure order was appropriate. The NYPD appealed the order.

Neither the NYPD nor the public is benefiting from this secrecy. The public has a right to know the extent to which these vans invade the average person’s privacy or pose a health risk. The questions of which technologies are used by law enforcement, and how, are proper subjects of democratic deliberation. There are undoubtedly operational details that cannot be made public, but that does not justify a level of secrecy that precludes public debate altogether.

Ultimately, the effectiveness of law enforcement depends on public trust. The irony is that the NYPD’s delay and lack of transparency has only served to diminish that trust, because by its actions the NYPD implies it has something to hide. A better course of action would be to share as much as possible, inviting the public to understand that while some operational details cannot be released, the NYPD wants the people it serves to be active participants in deciding how the police can best protect them.

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